Cerebrospinal fluid formation is being studied by radiological and related techniques. Th contributions of the various ventricular cavities and, if any, the subarachnoid pathways, are being measured. Radiological, physiological, structural and ultrastructural techniques are being used to study the morphology and function of the absorptive pathways. The effects of various obstructions of the C.S.F. pathways, and blood or high protein in the C.S.F. are to be studied. The studies of the endothelium of the villi or ganulations will be emphasized to determine the exact appearances of the cells under conditions that simulate those during normal function. Light microscopy, transmission electron microscopy, scanning electron microscopy and autoradiography will be used for these investigations. The mechanisms of ventricular enlargement will also be studied. The supplementary support requested is to provide partial salary support for the principal investigator for a 1 year period of sabbatical leave which would be spent in the research laboratory.